Packaging apparatus and techniques

ABSTRACT

Automatic packaging apparatus and methods for packaging food products such as bacon in evacuated or gas-filled packages. The disclosed machine is capable of convexly thermoforming two webs of packaging material into respective sets of pockets which are brought together in opposed positions to enclose the product. One preferred package made by the disclosed techniques comprises a transparent semi-rigid cup-like shell and a back-formed flexible film sealed over the shell opening. In operation of the disclosed machine, the product is loaded into the semi-rigid package shell from below, so that the upper sides of the product as introduced into the machine are pressed up against the inside surface of the shell, and after evacuation are held in that position by atmospheric pressure acting through the flexible film beneath the product. Thus, such upper sides of the product are visible through the transparent shell which serves as the display side of the package.

United States Patent Mahaffy et al.

[451 Apr. 23, 1974 [54] PACKAGING APPARATUS AND Primary Examiner-TravisS. McGehee TECHNIQUES I Attorney, Agent, or FirmBryan, Parmelee, Johnson[75] Inventors: Reid A. Mahaffy, Montclair; Joel A. & Bonmger Hamilton,Englewood; Wesley W. Pinney, Upper Montclair, all of NJ. [57] ABSTRACT 1D Automatic packagmg apparatus and methods for Asslgneei Mahaffy &Harder Engineering packaging food products such as bacon in evacuated py, TOtOWa, or gas-filled packages. The disclosed machine is capa- [22]Filed; May 31 1972 ble of convexly thermoforming two webs of packagingmaterial into respective sets of pockets which are PP 258,320 broughttogether in opposed positions to enclose the product. One preferredpackage made by the dis- [52] s Cl 53/184, 53/22 A, 53/ 12 A, closedtechniques comprises a transparent semi-rigid 53/167, 425/388 cup-likeshell and a back-formed flexible film sealed 51 int. Cl B65b 9/04, B65b31/02 Over the opehihg- Operation of the disclosed 58 Field of Search53/184, 112 A machine, the Product is loaded into the Semi-rigid spackage shell from below, so that the upper sides of [56] ReferencesCited the product as introduced into the machine are pressed up againstthe inside surface of the shell, and UNITED ST ATES PATENTS afterevacuation are held in that position by atmogllxll.t 53/513428; p ipressure i g h g the a l on neath the product. Thus, vsuch upper sidesof the prod- 2,935,828 5/1960 Mahaffy et al 53/ll2 A uct Visible throughthe transparent shell which serves as the display side of the package.

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EATENTEDAPR 2 1914 3.805486 sum on HF 12 PATENTEDAPR 23 um sum "as or 12MTENTEMPR 23 m4 sum 03 [1F 12 PATENTEUAPR 2a m SHEET '03 HF 12PATENTEDAPR 23 I974 sum 10 [1F 12 1 PACKAGING APPARATUS AND TECHNIQUESBACKGROUND OF THE INVENTION 1. Field of'the Invention This inventionrelates to packaging techniques, and especially to techniques useful inproducing vacuum or gas-filled packages for containing food products andthe like. More particularly, this invention relates in one principalaspect to improved packaging apparatus and methods suitable for makingpackages of a class exemplified by the disclosure of U.S. Pat. No.3,467,244.

2. Description of the Prior Art A variety of packaging machines havebeen proposed and used over the past decade or so for vacuum packagingof food products including cheese, luncheon meat, bacon, frankfurters,and the like. The machines which have been used include'rotary types,for example as shown in U.S. Pat. No. 2,888,787, and straight-linemachines such .as are shown in U.S. Pat. Nos. 3,061,984, 3,524,298 and3,545,163.

The packaging machines available heretofore have not been fullysatisfactory. In part, this is because the machines have not beencapable of packaging an adequately wide range of products. Specialproblems are presented in packaging certain products, particularlysliced bacon.

Such problems, for example, stem'from the fact that bacon typically issliced and simultaneously placed in shingled formation by machineshaving involuteshaped knives rotating on horizontal axes, arranged tocut the bacon fromabove. In order for these machines to slice baconcleanly, without tearing or separatingfat from lean portions, the knifemust enter from the lean (inside) side. Thus, the bacon necessarilyleaves the slicing machine with its lean side up, and it has generallybeen found to be good practice to convey andhandle the product with itslean side up, all of the way from the bacon press into the finishedpackage.

Now, it is well established that the final package should be so arrangedas to present to the customer a view of the lean side of the bacon,permitting customer inspection of the lean edges of the slices in a neatand uniform disposition. For best presentation, moreover, the displayside of the package should be the side which has been thermoformed intoa cup-like container for the bacon. 1

Some'packaging machines, even though capable making the especiallypreferred semi-rigid bacon package such as shown in U.S. Pat. No.3,467,244, form the semi-rigid display side downward (i.e., so that thecontainer opening faces up to receive the product). When such machinesare used for packaging bacon, the bacon must be inverted before loading,in order to dispose the lean edges against the display side. Thisinverting procedure has not been satisfactory, particularly due to thedangers of disrupting the shingle arrangement during the loadingoperation.

SUMMARY OF THE INVENTION Accordingly, it is one principal object of thepresent invention to provide a machine capable of producing modern-stylebacon packages, as described above, without requiring the bacon rashersto be inverted from the as-sliced, lean-up position to the lean-downposition prior to the packaging operations. Other principal objects ofthe invention include the development of imscribed hcreinbelow indetail, a packaging machine is provided wherein a continuous web offlexible film is thermoformed downwardly to make a series of upwardlyfacing cup-shaped receptacles into which the bacon is loaded from above,lean-side up. The loaded receptacles are moved horizontally to a packageassembly station to which also is directed, from a rotary turret abovethe station, a'continuous web of transparent semi-rigid plasticmaterial'thermoformed into a series of cup-shaped containers whichultimately will serve as the display side of the packages. Thesecontainers enter the assembly station with their openings facingdownwards, and mate with the flexible-film receptacles to fully enclosethe bacon product. The two webs there upon are sealed together to form acomposite evacuated package wherein the upper (lean) edges of the baconare forced up, by atmospheric pressure acting through the flexible film,against the inner surface of the semi-rigid container which thus servesto display the lean edges of the bacon to the customer.

To minimize the amount of required thermoforming of the thin, flexiblefilm, that film advantageously may be formed to a depth less than theproduct height, at least in certain regions. Portions of the productwould in these circumstances project above the web line. This howevercauses no problem in the disclosed machine, because the semi-rigid webis formed on the turret to a depth sufficient. to accommodate suchproduct projection. Thus, the unformed flange portions of both webs maybe brought together into a common plane, without wrinkling or gatheringof either, and may be heat-sealed together so as to effect the overallhermetic sealing of the package. Positive and precise positioning ofboth webs for high-quality scaling is achieved by the use of two sets ofintermeshing web clamps for the two webs, providing close positioningcontrol especially important when making packages with large-areapockets extending across a web having relatively great flexibility.

Other objects, aspects and advantages of the invention will in part bepointed out in, and in part apparent from, the following descriptionconsidered together with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a packagingmachine constructed as a preferred embodiment of the present invention;.

FIG. 2 illustrates one preferred package configuration made by themachine of FIG. 1;

FIG. 3 is an elevation view of the machine of FIG. 1;

FIG. 4 is a diagrammatic elevation view of the principal operatingcomponents of the machine;

FIG. 5 shows in perspective the two webs of packaging material advancingthrough the machine;

FIG. 6 is a detail section taken along lines 66 of FIG. 3, to show theflexible web being applied to the film clarnp;'

FIG. 7 is a detail section taken along line 77 of FIG. 3, to show theforming die for the flexible film;

FIG. 8 is a perspective view of the film clamp;

FIG. 9 is a vertical section showing details of the rotatable turret;

FIG. 10 is a detailed vertical section at the package assembly station;

FIG. 11 is a horizontal section, taken along line 11-11 of FIG. 10,showing the interleaved relationship of the two sets of clamps;

FIG. 12 is a vertical section, taken along line 1212 of FIG. 10;

FIG. 13 is a perspective view of the clamp fingers for the turret;

FIG. 14 is a detail section showing the initial seal arrangement;

FIG. 15 is a perspective view showing the initial seal outline;

FIG. 16 is a perspective view of the package-severing mechanism;

FIG. 17 is a vertical section showing elements of the evacuation andfinal seal stage;

FIG. 18 is a vertical cross-section taken along line l818 of FIG. 17;

FIG. 19 is a detailed vertical section showing aspects of the evacuationchamber;

FIG. 20 is a detailed horizontal section showing the outline of thelower evacuation die;

FIGS. 21 and 22 are vertical section views of a turret die;

FIG. 23 is a plan view of a'portion of the support means beneath theloaded receptacles;

FIG. 23a is a side view of a portion of the support means beneath theloaded receptacles; and

FIG. 24 is a vertical section showing the product control plate in theinitial seal member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG.1, there is shown a packaging machine 30 having a number of synchronizedmechanisms which, as will be described, operate in concert to produce aseries of packages like that illustrated in FIG. 2. This package issimilar in basic respects to that disclosed in U.S. Pat. No. 3,467,244,although certain differences will be noted hereinbelow.

The packaging machine 30 is provided in its lower right-hand region witha spindle 32 carrying a roll 34 of relatively thin plastic film ofpackaging material which is unwound as a continuous web by aconventional web-feed mechanism 33. This plastic film is directed (seealso FIGS. 3 and 4) to the upper reaches of an endless-chain conveyor 36arranged to carry the web with an intermittent indexing motion (to theleft in the drawings) past a series of stations where packagingoperations are performed during the dwell periods between indexes.

This conveyor 36 comprises two parallel, hollowroller chains eachadjacent one edge of the web 34, and each carrying a series of clampsets 40 (FIGS. 6 and 8) spaced apart uniformly along the chain. Eachclamp comprises spring-loaded jaw elements 42, 43 the tips of whichengage to grip the side margins of the web. The cylindrical portions ofupper elements 42 are loosely fitted within corresponding hollow rollersof chain 36, permitting axial movement of elements 42 as the clamp isopened and closed.

Pairs of lower elements 43 are integrally formed as part of a rockerplate 44 the top of which is curved to fit into a correspondingly curvedsupport element 45 to define an elongate pivot axis 46 for the rockerplate. Support element 45 is formed with L-shaped tabs 46A which areinserted into a base plate 47 fixedly secured to the chain 36. Theelements 42 are grooved on the top to fit with corresponding slots inrocker plate 44, so that elements 42 move horizontally as the platerotates about is pivot axis. Springs 48 surround elements 42 and urgethe plate 44 counterclockwise to tend to hold the gripper jaws shut.

Adjacent the conveyor 36, at a point preceding the point where the web34 is to be applied, a stationary ramp cam 49 is arranged to engage anarm 50 (forming part of the rocker plate 44) to rotate the plate 44about pivot axis 46. This shifts the elements 42 towards the chain 36,and also moves the lower elements 43 down and away (referring to FIGS. 6and 8) to permit the web to slip into position to be gripped by theclamp jaws. The lower elements are moved sufficiently in a lateraldirection that the film need not be bent or deflected prior to entryinto the clamp.

After the web 34 has been properly positioned, the cam 49 ramps thelower element back against the upper element, tightly gripping theplastic film under the compressive force of spring 48. The jaws grip theplastic film in the plane of the web and thus do not tend to distort thefilm. This clamp arrangement also is advantageous because it isself-actuating in the sense that any tendency of the film to pull awayfrom the clamp causes the jaws to be forced together and bite the filmever more tightly.

Referring again to FIGS. 3 and 4, and also to FIG. 7, the conveyor 36carries the web 34 past a two-stage, vertically-reciprocablethermoforming means comprising a heating station 52 and a formingstation 54. This thermoforming operation is basically similar to thatdisclosed in U.S. Pat. No. 3,524,298, and thus will not be described ingreat detail herein.

To summarize the thermoforming operation briefly, in the heating station52 a heated platen is brought up to the web line and a seal is madebetween it and the film through contact with a fixed back-up platenabove the web. Vacuum is drawn through the heated platen to bring thefilm into contact with the heated surface, to raise the temperature ofthe film to a level suitable for stretch-forming. At the end of thedwell cycle, this heated platen is lowered,'and the film is indexed tothe next station 54 where a water-cooled forming die 56 is brought up tothe underside of the film.

Vacuum is applied to this die 56 to cause the heated film to be forceddownward by atmospheric pressure and conform to the shape of the diecavity. The film is thereby stretched into a cup-shaped pocket 58adapted to serve as a receptacle for the product. The die 56 preferablyincludes side troughs 56A adapted to stretch the side margins of thefilm more than the central regions, thereby to form the special ear-likeelements, disclosed in U.S. Pat. No. 3,467,244, which extend along thesides of the product in the final package.

The shape of the formed receptacle 58 should be such as to allow theproduct to be placed into it and effectively locate the product forfurther operations. For bacon packaging, the die 56 is arranged tostretch the web, in the marginal regions at the periphery of thereceptacle, to an appropriate depth, and with suitable contours, topermit each thermoformed receptacle to embrace all sections and contoursof the bacon rashers (as illustrated in FIG. 5 of U.S. Pat. No.3,467,244),

taking into account the fact that the actual size and configuration ofthe shingled bacon varies somewhat from rasher to rasher. Thus, thereceptacle should be formed to properly contain the most extreme baconarrangement (i.e., extreme as to size and shape) which may be deliveredfrom the slicing machine. The great majority of 'rashers, which are lessextreme, will automatically be accommodated by the self-adjustingcharacteristic of the package, discussed subsequently.

As the web 34 emerges from the forming station 54 (FIG. 4), it moves outunder a product loader 59 arranged automatically to deposit the slicedbacon into the receptacles 58. This product loader may be substantiallythe same as that shown in US. Pat. No. 3,354,613, and thus will not bedescribed in detail herein. It maybe noted, however, that in such aloader, the advancing movement of the product conveyor is continuous,but its speed is varied, synchronously with the operation of theintermittent-motion web-conveyor 36, in such a way as to insure that theproduct speed matches the receptacle speed at the instant of transfer.

The loaded receptacles 58 are indexed to the left, along the horizontalpath of movement of the chain conveyor 36, to a package assembly andinitial seal station 60. Immediately above that station is a rotatable,multi-faceted drum or turret 62 which delivers to station 60 acontinuous web 64 of heavy-gauge plastic formed into semi-rigidcontainers 66 (see also FIG. 5)

adapted'to mate with the formed receptacles 58 to completely enclose theproduct to be packaged.

The assembly station 60 includes a verticallyreciprocable initial sealmember 68 (see also FIGS. 14 and carrying an impulse-type seal element-70. This seal member is moved up during the dwell period by a lowerreciprocating bed 72. (This lower bed also serves to reciprocate thevarious other movable packaging components located beneath the webline.) At the end of the up-stroke, the seal member 68 is pressed upagainst the lower web 34 by internal spring-loading (illustrated in FIG.4 at 74). The impulse seal element 70 then is activated to apply to theflange areas surrounding the lower receptacle 58 sufficient heat to sealthem to the flange areas of the semi-rigid containers 66 around theentire periphery, except for one region 76 through which the package isto be evacuated.

The turret 62 is drivingly connected to the conveyor 36 by a series ofcoupling elements 78 which engage the conveyor chain. Thus, the turretis rotated with an intermittent indexing movement exactly synchronizedwith that of the horizontal conveyor. As the turret rotates, it receivesthe semi-rigid plastic film 64 from a roll 80 which is unwound by aconventional web-feed mechanism 82, e.g., identical to the lowerweb-feed 33.

Referring now also to FIG. 9, it will be seen that the turret 62isprovided around itsperiphery with a series of forming dies 84 10, inthis embodiment) the cavities of which are shaped to match theconfiguration of the preferred container 66. During each indexing step,an empty die moves into position under a fresh portion of the web 64. Atthe start of the following dwell period, a pressure plate86 is swungdown to press the web into proper position over the die. Thereafter, apair of toggle-actuators 88 adjacentthe sides of the turret 62 arethrust forward by a control mechanism 90 (including a chain-driveneccentric 92) so as to actuate corresponding toggle linkages 94 (one seton each end of each die). These toggle-linkages in turn shiftcorresponding die clamps 96 into position to hold the web tightly overthe die.

The die clamps 96 comprise a set of spaced, parallel, elongate andspringy clamp fingers 100 (see also FIG. 13) the tips of which arecurved over to a position to be pressed tightly against the turret framealongside the side wall of the die 84. The toggle-linkage 94 is anovercenter mechanism, with springs 102 arranged to develop inthe closedposition a force pressing the clamp fingers against the turret frame, soas to pin the edge of the web tightly in position overlying the die. Inthe open position of the linkage 94, the springs 102 serve to hold theclamp fingers away from the die.

The plastic web 64 is carried by the indexing movement of the turret 62beneath a retractable radiant heater which, in three successive diestations, heats the plastic to forming temperature. After indexing fromunder the heater, vacuum is applied to the die cavity under the film,stretching the heated film down against the walls of the cavity. Thevacuum is maintained during subsequent indexing, to assure that the filmcools sufficiently in its proper shape. The vacuum to the dies iscontrolled by a rotary slide valve (not shown) adjacent the hub of theturret, and to which all of the die cavities are connected by suitablevacuum lines. Each die also is water cooled. Vacuum and waterconnections are made automatically to the die when the die is secured inplace on the turret, as by means of a quarterturn fastener.

Thermoforming dies must provide certain characteristics in order toperform their intended function properly. For example, the dies musthave an interior profile corresponding precisely to the part to beformed, and the surfaces must be capable of withstanding considerableheat from the web, without sticking to the web. The heat of the web alsomust be absorbed quickly, so as to cool the film to setting temperature.In the areas where heat seals are to be made after forming, the dieshould be covered by an unbroken resilient sealing back-up material. Inaddition to these generally fundamental requirements, the dies should beadaptedfor quick and easy replacement, and should be reasonablyeconomical to manufacture. Moreover, the dies advantageously should becapable of forming relatively complex shapes (such as the trapezoidalcontainer 66 of FIG. 2), with a highly transparent, blemish-free filmsurface, to enhance the customers ability to inspect the product. 4

These desirable results are achieved in accordance with one aspect ofthe present invention by molding to the surfaces of the dies 84 a thinlayer of resilient material 120, e.g., silicone rubber, integrallyextending throughout the cavity region, and also over the flangesurfaces where the rubber serves as a heat-seal back-up bead 122 (FIG.21). The rubber covering is molded to the precise interior dimensionsrequired. The metal (aluminum) surfaces of the die, beneath the rubber,thus need not be held within close tolerances, and may be as-cast, orrough-machined, for example to a tolerance of 1- 1/64 inch. The rubberlayer is sufficiently thin to conduct heat rapidly from the formed webto the metal of the die, where the heat is further dissipated by watercooling. The rubber thickness may, for example, be between l/l6 inch and3/32 inch.

The rubber bead 122, on the flange surfaces, should (for the disclosedpackage) be effectively planar, e.g., flat within .005 inch (totalindicator reading),'and parallel to the back surfaces of the die. Thebead particularly should be free of nicks, holes and foreign matter. Therubber within the cavity may be formed with small holes communicatingwith the chamber 124 beneath he die cavity (which chamber is suppliedwith vacuum by the rotary slide valve at the appropriate time in thesequence of operations), in order to vacuumize the die to draw theheated web into the cavity by atmospheric pressure.

The rubber layer 120 may be molded directly into the die cavity byvarious techniques. For example, a quantity of rubber may be depositedapproximately in the center of the cavity, and a precisely machined coremember (illustrated at 126) pressed into the cavity, together withapplication of heat, to compress the rubber and force it over all of thedie surfaces including the flange areas around the cavity. The metalsurfaces of the die should, before depositing the rubber, have appliedthereto an adhesive composition to effect a bond between the metal andthe silicon rubber. The bond should have a strength exceeding the tearstrength of the rubber.

The core member 126, made for example from aluminum, is preciselymachined to match the exact contours of the part to be formed, i.e.,container 66, in this case. It may be noted that only one precisionmachining operation is necessary, since the single core can be used fora number of dies. Thus this arrangement avoids costly machiningoperations required in prior types of dies wherein bare metal surfacesare presented to the hot drawn web. The disclosed arrangement also issuperior to the use of thick die-filler blocks which, for example, donot conduct heat away at a sufficient rate to be satisfactory in manyapplications, such as in forming semi-rigid film.

Moreover, in the present arrangement, if any part of the bead 126becomes damaged, or for any reason requires repair, the entire rubbercovering may be stripped and replaced. The desired interior contours,dimensions, and surface finish result from the original mold which needbe machined only once. The result is a very satisfactory and economicaldie construction.

Returning now to the operational description, the indexing movement ofthe turret 62 brings each semirigid container 66, completely formed,into register with 'a corresponding loaded receptacle 58 at the assemblystation 60. The container 66 is brought down at an angle with respect tothe horizontal web line, and moves into station 60 simultaneously withthe associated loaded receptacle 58, so that there is no interferencebetween the two even when the product extends above the flange regionsof the receptacle 58.

During the indexing movement, the coupling elements 78 force the chain36 downwards a small distance. The chains are supported by spring-loadedmounts to accommodate this motion.

At the end of the indexing movement, the flanges of the upwardly facingreceptacle 58 and the flanges of the downwardly facing container 66 areparallel and effectively in the same plane, prior to sealing asdescribed above.

Important to successful sealing is the positive positioning of both websby the respective clamps 40 and 96. Thereby, accurate control over thewebs is assured to provide that the two sets of formed pockets arecorrectly related when sealing takes place, resulting in a good seal,particularly without problems from wrinkling. As shown most clearly inFIGS. 11 and 12, the clamp elements 42, 43 and the clamp fingers areinterleaved, in staggered fashion, along the main machine direction(i.e., parallel to the edge of the web 34) to allow concurrent,continuous gripping of both webs, yet without any mechanicalinterference between the respective components.

During the dwell period, the sealing member 68 is brought up to pressthe two webs 34 and 64 against a die 84 of the turret 62, and once thesealing member is seated, its spring-loading force against the diepositively holds the two webs tightly in position for the sealingoperation. Accordingly, referring to FIG. 12, at this time the clampfingers 100 are released from engagement with web 64. This release iseffected by a stud carried by an upper bed 132 of the verticalreciprocation mechanism of the machine, and which is reciprocated (bydrive linkages shown in FIG. 3) in synchronism with the lower bed 72(see above) but opposite thereto, with both beds being maintainedhorizontal at all times.

At the end of the dwell period, i.e., after partial or preliminarysealing has been completed between receptacle 58 and container 66, theseal member 68 is retracted downwards. The partially completed packagethen is indexed two steps to the left where it is engaged by theoperating elements of an evacuation and final seal station 136. Theseelements comprise upper and lower vacuum chambers 138, which are movedby beds 72 and 132 into position surrounding and sealing off the packageassembly from outside atmosphere.

,The chambers 138, 140 are both connected in common to a vacuum valve142 which, when the chambers are in closed position, is actuated by cammechanisms to evacuate above and below the package. The interior of thepackage also is evacuated through a previously formed evacuation slot144 (see FIG. 19) in the lower web, the air exiting through a passage146 forming part of the lower vacuum chamber, and communicating with themain vacuum line to that chamber. The evacuation slot is formed inconventional fashion by a slitting knife 148 (FIGS. 3 and 7) carried bythe upper bed 132 in a position just preceding assembly station 60.

The lower vacuum chamber 140 contains a die-filler 150 (FIG. 19) whichforces the receptacle 58 and the product up towards the container 66,preferably positioning the product very near to the top of thecontainer. This elevation of the product prior to evacuation has beenfound to be highly desirable and effective in achieving high performancecapabilities. The upper vacuum chamber 138 also contains a die-filler152 which matches the shape of the semi-rigid container. Bothdie-fillers reduce the amount of air which must be drawn out duringevacuation.

At the end of the evacuation cycle, gas may be introduced to the packagethrough a gas tube (not shown) leading to a region adjacent to theevacuation passage 146.

When evacuation or gassing has been completed, the evacuation slot issealed shut by a reciprocable, heated final seal platen 160, in anarrangement somewhat similar to that shown in U.S. Pat. No. 3,524,298.

After sealing, both chambers 138, 140 are vented to atmosphere.Preferably the lower chamber is vented first, followed a short timelater by venting of the upper chamber. The atmospheric pressure forcesthe lower film 34 up against the product, thereby pressing the productagainst the upper surface of the container 66 with a force dependentupon the degree of evacuation and the extent of gas-filling, if any. Theflexible lower film is tightly forced into the container interior,extending down along the side walls of the container, and filling anyvoid areas which may remain between the product and the container walls.The performing of the lower web 34, to make the pockets 58, provides thenecessary stretched marginal film regions, i.e., immediately inboard ofthe container walls, to assure a good close fit.

It particularly may be noted that with this arrangement, the volume ofthe package automatically adjusts to the volume of the product, thusassuring consistently good packages even where there is considerablevariation in product size or contour, from unit to unit, as thereparticularly is with sliced bacon.

After the vacuum chambers 138, 140 have separated, at the end of thedwell period, the package continues to index on its horizontal pathuntil it reaches a boardapplication station 166. Below this station is aboard magazine 168, containing a stack of stiff, flat cardboard elements170 which are lifted, one at a time, by a chainfeeder 172 and carried upto station 166 for application to the package to serve as a stiffprotective member adjacent and parallel to the formed flexible filmportion 58. The board is positioned in register with the package, andduring the dwell of the machine a heat seal bar is brought up fromunderneath to activate a heat seal coating on the board, so as to sealthe board to the flexible web entirely around the periphery of thepackage.

After the board is sealed to the film 34, the clamps 40 are momentarilyopened and then closed, to allow the clamps to grip the semi-rigid weband the board as parts of the complete package assembly. At the stationnext after the sealing station, water-cooled member 174 is brought upagainst the sealed regions of the board to cool the board and set thesealant prior to further processing.

Completed packages are indexed further to the left and, near the end ofthe upper reaches of the conveyor 36, the clamps 40 are again rampedopen to release the line of completed packages. Continuing movement ofthe unreleased packages pushes the released packages forward, aided ifnecessary by a small auxiliary conveyor beneath the web line. Thereleased packages are thereby moved into a cut-off station 180 (FIG. 16)where the packages are severed from one another, and simultaneously thepackage corners are trimmed with a smooth round curve. This cuttingoperation is performed by a rolling cutter drum 182 formed on itsperipheral cylindrical surface with a cutting edge 184 the ends of whichare bifurcated to define rounded curves for the corner trimming.

At the start of the dwell period, a back-up platen 186 is reciprocateddown into the flange area of the upper web 64, between adjacentcontainers 66. This reciprocating motion is produced by a linkagemechanism including two links 188, 190 and an air-cylinder 192 whichmoves the link coupling 194 to the left to force the links to asubstantially vertical lock position. This movement pulls down thesupport shafts 196 for the platen 186, and at the end of the movementthe platen is locked in place (due to the positional relationship of thelinks) to permit the application of great cutting force withoutsignificant deflection of the opposed parts.

Once the linkage mechanism 188, 190 has been locked in position,conventional means (not shown in detail) are actuated to roll the cutter182 in a crossmachine direction, under the flange area between twopackages, so that the cutting edge 184 bites through the two webs 34 and64 to sever the package. The backing board is performed with curvedcorners, so that it is not cut at this time. The severed packages may befed out of the machine by conventional conveyor means.

For machines of the type described which are to be operated atrelatively high speed, e.g., 40 or so indexes per minute, there may be atendency for the product to slip'out of the receptacle 58 prior to theinitial seal station 60, due to acceleration and deceleration at eachindex. This may particularly be a problem where the pockets 58 have adepth less than the product height, an arrangement which is desirable inorder to avoid over-thinning of the plastic film. It also mayparticularly be a problem with slippery products, such as bacon,especially where the edges of the pockets 58 slope gently in the machinedirection, thereby giving a somewhat ramp-like formation where theproduct can slide too easily. In addition, there can be a problem withrelatively heavy products which cause the formed pockets 58 to sag, anddevelop a pendulum-like swinging as the indexing motion stops and startsat high speed.

To avoid such difficulties, the machine 30 may with advantage beprovided with special means to engage the loaded pockets 58 and preventor minimize relative movement between the product and the receptacles.In the present embodiment (referring now to FIGS. 4 and 23), there isprovided beneath the loaded receptacles 58 a conveyor-like productcontrol structure generally indicated at 200, and comprising a train ofelements including a set of maincrossbars 202 located directly beneaththe flange areas of the web 34, and intermediate sets of support slats204 located beneath the pockets 58. This train of elements is carried bya pair of chains 206 driven in synchronism with the chain conveyor 36.

The main bars 202 extend up into the region alongside of the verticalend walls of the pockets 58, and serve as barriers to any movement ofthe contained products, in the machine direction, relative to themovement of the conveyor 36. Thus, the products are kept positivelywithin the confines of the cavities defined by the pockets during thepassage of the loaded pockets to the assembly station 60. Also duringthis time, the lower support slats 204 prevent the bottom of the pocketsfrom sagging significantly, under the weight of the product.

The product control structure 200 terminates adjacent the assemblystation 60, because of the presence of the initial s'eal member 68. Toprevent excessive product movement within the assembly station position,as the indexing movement stops, the initial seal member may be providedwith additional special means which restrains forward motion of theproduct at the end of indexing, without interfering with subsequentforward movement of the partially assembled package after the initialseal has been completed.-

Referring now to FIG. 24, a preferred embodiment of such restrainingmeans comprises a plate 210 pivotally mounted at 212 on the top of avertical support 214 which is integral with the seal member 68, i.e., sothat the two reciprocate together during the dwell period. This plate210 is urged in clockwise direction by a spring 216 and, during indexingmovement, takes the tilted position shown, against a stop 218.

A product-filled pocket 58 is shown in FIG. 24 approaching the assemblystation 60, that is, in a position partway through the indexingmovement. Since the pocket has left the support control structure 200,its bottom will sag somewhat, under the weight of the product. The plate210 is so positioned, vertically, that a portion of the plate is locatedabove the lower surface of the filled pocket 58. Thus, as the pocketindexes into the station 60, it will strike the plate and tend to rotateit counterclockwise against the spring 216, ultimately repositioning theplate in horizontal condition.

This rotation of the tilted plate 210 against its spring loading absorbsenergy from the advancing product, and thereby tends to prevent forwardmovement of the product beyond the movement of conveyor 36. Thus theproduct is prevented from sliding up into the area of the flangesforward of the pocket 58. Once the seal has been made, there is nopossibility of product movement out of the pocket during subsequentindexing.

For some applications, it may be desirable to arrange the support 214for vertical movement, e.g., by utilizing a telescoping or pistonconstruction for the support. Thus, if the product weight is sufficient,the support can move down a short distance prior to, or simultaneouslywith, the upward movement of the sealing member 68.

The presently preferred bacon package 250 shown in FIG. 2 comprises thesemi-rigid, transparent container 66, serving as the display top for thepackage, the flexible back-formed plastic cover film 34 (hermeticallysealing the evacuated interior), and the flat, stiff cardboardprotective member 170, as the base of the package. The seal between theboard 170 and the flexible film preferably is stronger than the sealbetween the flexible film and the container 66, in order to enhance thecustomers ability to open the package by breaking the seal between thetwo plastic films, using the backing board to aid in applying a pullingforce to the flexible film.

One advantageous way of opening the package is to break the seal betweenthe two plastic films along the two short sides and one line side, andthen pivot the top back along a line adjacent and parallel to theremaining, unbroken seal line to gain access to the bacon. After thepackage has been opened, and a portion of the bacon removed, theremainder of the bacon can be placed, or left on the compositeboard/film (still sealed together as a unit), with the top swung backinto place covering the product. Thus the remaining bacon is stillprotected on all sides by relatively rigid elements, and the compositeboard/film unit can act as a serving base or platter for the remainingportion of the product.

To insure that the top stays firmly in place after the seal is broken,and the package subsequently reclosed, the flange corners of thesemi-rigid container 66, and the film 34, are slit at 252 to receive atab 254 (see FIG. 5) pre-formed in the corresponding corners of theboard 170. The tabs can be pressed out and inserted up through the slits252 after the cover 66 has been swung backdown over the product. Theside walls of the cover 66 are slightly angled at 256 to providesufficient area for the reclosure slits.

These slits 252 are cut through the two webs 34 and 64 by knives 260carried along with the lower evacua tion chamber (see FIG. 19), andwhich cooperate with corresponding elements moving down from above toeffect an arc-shaped cut readily adapted to receive the cardboard tab254.

The machine disclosed can be used to make other types of packages. Forexample, the machine can make packages of two convexly thermoformed websof flexible packaging material, i.e., by using the turret 62 to makepockets from flexible film rather than semi-rigid film. The machine alsocan be used to make packages of two convexly formed webs of semi-rigidmaterial, or the lower web can be semi-rigid and the top web flexible,if desired.

For some applications, the two convexly formed pockets could each bedrawn with suitable depth and contour to receive and contain acorresponding segment of the product, e.g., the upper half of theproduct contained in the upper pocket, and the lower half of the productin the lower pocket. With such an arrangement the sealing flange line islocated half-way between the top and bottom of the package, rather than,as in the disclosed package, at the very bottom of the package. In sucha modified package, the combined depth of the two opposed pocketsadvantageously would be so dimensioned as to provide slightly morevolume than required for the maximum-sized article to be packaged, i.e.,where the article size varies, as with bacon. Such a package normallywould be made of all flexible material, although it is possible to makesuch a package using semi-rigid material for one or both of the opposedpockets. It also is possible to make vacuum packages with one flexibleand one rigid web wherein the flexible web in its final position may liepartially above and partially below the web line.

Although preferred embodiments of the invention have been describedhereinabove in detail, it is to be understood that this is for thepurpose of illustrating the invention and should not be construed asnecessarily limiting of the invention, it being well recognized thatthose skilled in the art may make numerous changes to suit differentrequirements while still practicing the invention claimed hereinafter.For example, although the particular turret arrangement describedhereinabove is advantageous, and preferred, it is evident that othermeans can be devised to perform the basic required functions.

We claim:

1. An automatic packaging machine adapted to make hermetically sealedpackages for food products and the like, comprising:

a first conveyor for transporting a first web of packaging materialalong a first path;

first forming means for thermoforming said packaging material into afirst series of cup-like pockets;

said first path having, subsequent to said first forming means, aportion which extends in a generally horizontal direction and whereinsaid pockets are presented with their openings facing upwards adapted toreceive products to be packaged;

a package assembly station adjacent said generally horizontal portion ofsaid first-path;

a rotary conveyor above said package assembly station to transport asecond web of packaging material from a position above said assemblystation along a second path comprising a curved portion leading fromsaid position down into said station and joining said first web at anangle with respect thereto;

said rotary conveyor including second forming means operable on saidsecond web while it is passing along said second path curved portion forthermoforming said second web into a second set of cuplike pocketsadapted to mate with said first set of pockets at said assembly stationto define package assemblies;

means at or subsequent to said package assembly station for sealing saidfirst and second webs together to form sealed packages;

first clamp means on said first conveyor for positively gripping saidfirst web of packaging material while moving along said second pathportion to assure precise control over the advancing movement of saidfirst web; and

second clamp means on said second conveyor for positively gripping saidsecond web of packaging material to assure precise control over theadvancing movement thereof into said assembly station so as to provideexact synchronism with the first web of packaging material entering saidassembly station from said second path portion, thereby to effectpositive alignment of the corresponding pairs of pockets of said firstand second sets and to accurately-seal said corresponding pairs ofpockets with the product in the container formed by each correspondingpocket pair. v

2. An automatic packaging machine adapted to make hermetically sealedpackages for food products and the like, comprising:

a first conveyor for transportimg a first web of packaging materialalong a first path;

a first set of clamp elements on said first conveyor and spaced alongthe side edges of said first web to hold it in position;

first forming means for thermoforming saidpackaging material into afirst series of cup-like pockets;

said first path having, subsequent to said first forming means, aportion which extends in a generally hori-' I zontal direction andwherein said pockets are presented with their openings facing upwardsadapted to receive products to be packaged;

a package assembly station adjacent said generally horizontal portion ofsaid first path;

a rotary conveyor above said package assembly station to transport asecond web of packaging material along a second path leadinginto saidstation and joining said first web at an angle with respectsecondforming means for thermoforming said second web into a second set ofcup-like pockets adapted to mate with said first set of pockets at saidassembly station to define package assemblies; and

means at or subsequent to said package assembly station for sealing saidfirst and second webs together to form sealed packages.

3. Packaging apparatus comprising:

a first conveyor for transporting a first web of packaging materialalong a first path to a package as sembly station, said path beinggenerally horizontal at least in the portion thereof immediatelypreceding said assembly station;

said first conveyor comprising a plurality of edge clamps mounted in anendless loop and arranged to grip the side edges of said first web;

said edge clamps each comprising first and second elements forming agripping jaw at the ends thereof;

means pivotally mounting at least one of said elements and operable whenthe jaw is opened to provide for retractile movement of one element awayfrom the side edge of the web;

said one element being pivotally mounted at a point vertically offsetfrom the axis of said other element and in a position between said chainand the end of the jaw;

said other element being movably mounted with rea first forming stationfor thermoforming said first web into a first set of container pocketsthe openings of which face upwards in said horizontal path portion;

a second conveyor for transporting a second web of packaging materialalong a second path distinct from said first path and leading to saidpackage assembly station, the portion of said second path immediatelypreceding said assembly station extending downwards towards said firstpath at an angle with respect thereto;

a second forming station adjacent said second path for thermoformingsaid second web into a second set of container pockets the openings ofwhich face downwards at said assembly station, thereby to mate with saidfirst set of container pockets to define package assemblies; and

sealing means for securing together the first and second sets of matedcontainer pockets.

4. Apparatus as claimed in claim 3 wherein said one element comprisestwo sections;

one section engaging said other element as part of said jaw andextending generally away from the end of said jaw to a region of joinderwith the other section;

said other section extending transversely across the axis of said otherelement to the pivot point, and engaging said other element to providefor motion thereof as said one element is moved.

5. Packaging apparatus comprising:

first forming means to thermoform a first continuous web of packagingmaterial into a first series of cupshaped containers:

second forming means to thermoform a second continuous web of packagingmaterial into a second

1. An automatic packaging machine adapted to make hermetically sealedpackages for food products and the like, comprising: a first conveyorfor transporting a first web of packaging material along a first path;first forming means for thermoforming said packaging material into afirst series of cup-like pockets; said first path having, subsequent tosaid first forming means, a portion which extends in a generallyhorizontal direction and wherein said pockets are presented with theiropenings facing upwards adapted to receive products to be packaged; apackage assembly station adjacent said generally horizontal portion ofsaid first path; a rotary conveyor above said package assembly stationto transport a second web of packaging material from a position abovesaid assembly station along a second path comprising a curved portionleading from said position down into said station and joining said firstweb at an angle with respect thereto; said rotary conveyor includingsecond forming means operable on said second web while it is passingalong said second path curved portion for thermoforming said second webinto a second set of cup-like pockets adapted to mate with said firstset of pockets at said assembly station to define package assemblies;means at or subsequent to said package assembly station for sealing saidfirst and second webs together to form sealed packages; first clampmeans on said first conveyor for positively gripping said first web ofpackaging material while moving along said second path portion to assureprecise control over the advancing movement of said first web; andsecond clamp means on said second conveyor for positively gripping saidsecond web of packaging material to assure precise control over theadvancing movement thereof into said assembly station so as to provideexact synchronism with the first web of packaging material entering saidassembly station from said second path portion, thereby to effectpositive alignment of the corresponding pairs of pockets of said firstand second sets and to accurately seal said corresponding pairs ofpockets with the product in the container formed by each correspondingpocket pair.
 2. An automatic packaging machine adapted to makehermetically sealed packages for food products and the like, comprising:a first conveyor for transportimg a first web of packaging materialalong a first path; a first set of clamp elements on said first cOnveyorand spaced along the side edges of said first web to hold it inposition; first forming means for thermoforming said packaging materialinto a first series of cup-like pockets; said first path having,subsequent to said first forming means, a portion which extends in agenerally horizontal direction and wherein said pockets are presentedwith their openings facing upwards adapted to receive products to bepackaged; a package assembly station adjacent said generally horizontalportion of said first path; a rotary conveyor above said packageassembly station to transport a second web of packaging material along asecond path leading into said station and joining said first web at anangle with respect thereto; the lowermost portion of said rotaryconveyor being aligned with said first path portion to maintain saidsecond web of material effectively coplanar with said first web withinsaid assembly station; a second set of clamp elements on said rotaryconveyor and spaced apart along the side edges of said second web tohold it in position; said first and sedond sets of clamp elements beingeffectively in the same plane at said assembly and interleaved toprevent interference; second forming means for thermoforming said secondweb into a second set of cup-like pockets adapted to mate with saidfirst set of pockets at said assembly station to define packageassemblies; and means at or subsequent to said package assembly stationfor sealing said first and second webs together to form sealed packages.3. Packaging apparatus comprising: a first conveyor for transporting afirst web of packaging material along a first path to a package assemblystation, said path being generally horizontal at least in the portionthereof immediately preceding said assembly station; said first conveyorcomprising a plurality of edge clamps mounted in an endless loop andarranged to grip the side edges of said first web; said edge clamps eachcomprising first and second elements forming a gripping jaw at the endsthereof; means pivotally mounting at least one of said elements andoperable when the jaw is opened to provide for retractile movement ofone element away from the side edge of the web; said one element beingpivotally mounted at a point vertically offset from the axis of saidother element and in a position between said chain and the end of thejaw; said other element being movably mounted with respect to saidchain, and arranged to move with said one element away from said web asthe clamp is opened; a first forming station for thermoforming saidfirst web into a first set of container pockets the openings of whichface upwards in said horizontal path portion; a second conveyor fortransporting a second web of packaging material along a second pathdistinct from said first path and leading to said package assemblystation, the portion of said second path immediately preceding saidassembly station extending downwards towards said first path at an anglewith respect thereto; a second forming station adjacent said second pathfor thermoforming said second web into a second set of container pocketsthe openings of which face downwards at said assembly station, therebyto mate with said first set of container pockets to define packageassemblies; and sealing means for securing together the first and secondsets of mated container pockets.
 4. Apparatus as claimed in claim 3wherein said one element comprises two sections; one section engagingsaid other element as part of said jaw and extending generally away fromthe end of said jaw to a region of joinder with the other section; saidother section extending transversely across the axis of said otherelement to the pivot point, and engaging said other element to providefor motion thereof as said one element is moved.
 5. Packaging apparatuscomprising: first forming means to thermoform a first continuous web ofpaCkaging material into a first series of cup-shaped containers: secondforming means to thermoform a second continuous web of packagingmaterial into a second series of cup-shaped containers adapted to matewith said first series of containers to define package assemblies; firstconveyor means to carry said first web along a first path extending in agenerally horizontal direction with said first series of containersdisposed with their openings facing upwards to receive products loadedfrom above the web line; second conveyor means to carry said second webwith said second series of cup-shaped containers along a second pathwhich extends down towards said first path at an angle with respectthereto and joins said first path at a package assembly station wheresaid second series of containers are placed, opening downwards, oversaid first series of containers; means at or subsequent to said assemblystation for sealing said two series of containers together; said secondconveyor means comprising die means defining a series of cavities toreceive said second series of containers; and said die means comprisingrough-shaped rigid material covered with a thin continuous sheet ofprecision-cast resilient material adhesively secured to said rigidmaterial and establishing the required container shape, whereby toaccommodate thermoforming said second web of packaging material in thecavities established by said sheet of resilient material.
 6. Apparatusas claimed in claim 5, wherein said second conveyor means comprises arotatable polygonal structure presenting a series of cavities at itsouter periphery; a single integral sheet of said resilient materialcovering the interior of each cavity and, as well, covering the flangeareas immediately surrounding each cavity to serve as heat-seal beads.7. Apparatus as claimed in claim 5, wherein said sheet of resilientmaterial has a substantially uniform thickness throughout.
 8. Apparatusas claimed in claim 5, wherein said sheet of resilient material ismolded about a precision-formed core shaped to match the desiredcontainers.
 9. In packaging apparatus of the type wherein a web ofpackaging material is transported with an intermittent indexing motionby edge supports which grip the side edges of the web so as to suspendthe central web portions therebetween, and wherein means are providedfor forming the central web portions into downwardly extending pocketsto be loaded with product for conveyance to a subsequent station wherefurther packaging operations are performed; that improvement foreffecting controlled product conveyance as the loaded pocket is shiftedinto said station comprising: a restraining element at said station;means mounting said element in the path of motion of said loaded pocketso that said pocket engages said element near the end of its indexingmotion; said mounting means providing for movement of said element outof the path of said pocket after contact therewith whereby said pocketcan be indexed further without interference.
 10. Apparatus as claimed inclaim 9, wherein said restraining element is a plate pivotally mountedfor rotary motion as it is struck by the advancing pocket.
 11. Apparatusas claimed in claim 9, including a spring urging said plate in adirection against a stop, to provide a tilt angle resulting in aglancing blow when struck by the pocket.
 12. Packaging apparatuscomprising: a first conveyor for transporting a first web of packagingmaterial along a first path to a package assembly station, said pathbeing generally horizontal at least in the portion thereof immediatelypreceding said assembly station; a first set of edge clamps forming partof said first conveyor and arranged to grip the side edges of said firstweb to provide positve and precisely controlled movement thereof withsaid first conveyor; a second conveyor for transporting a second web ofpackaging material along a second path distincT from said first path andleading to said package assembly station, the portion of said secondpath immediately preceding said assembly station extending downwardstowards said first path at an angle with respect thereto; a second setof edge clamps forming part of said second conveyor to grip the sideedges of said second web to provide positive and precisely controlledmovement thereof with with the advancing movement of said first web asthe two webs enter said package assembly station; a forming stationadjacent at least one of said paths for thermoforming the correspondingweb into a set of container pockets to be advanced into said assemblystation for assembly with the other web to define package assemblies;and sealing means for securing together the first and second webs toform hermetically sealed packages.
 13. Apparatus as claimed in claim 12,wherein said first set of edge clamps grips said first web as itadvances through said assembly station and to a position beyond saidassembly station; said sealing means comprising means located at saidposition beyond said assembly station for effecting a complete seal ofthe packages advanced thereto by said first conveyor edge clamps.